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Anyone ever use sulfamic acid to force a patina? Looks like the patina it forces can be jet black and if left on long enough it will even patina stainless steel.

Its a pretty heavy duty acid. A lot of silver polish and tarnish removers have it as an active ingredient as well.

_________________There's an old Italian saying, don't burn your tongue on another man's soup.

Tall Dark and Swarfy

Post subject: Re: Sulfamic Acid

Posted: Mon May 26, 2014 1:07 pm

Joined: Wed Feb 20, 2013 2:22 amPosts: 987

I've seen varying opinions on whether the patina formed by sulfamic acid is indeed protective. If I was going that route I would probably try rust blue, aka Belgian blue. Stay away from nitre blue due to the high temps required.

Cheers,

Rick

Jason B.

Post subject: Re: Sulfamic Acid

Posted: Mon May 26, 2014 7:07 pm

Joined: Tue May 29, 2012 12:29 amPosts: 1129

Ferric chloride

whosthebestcop

Post subject: Re: Sulfamic Acid

Posted: Mon May 26, 2014 10:53 pm

Joined: Mon May 19, 2014 1:52 amPosts: 448Location: Philly

That stuff sounds even better. I would probably just stick with boiled apple cider vinegar I'm not a chemist hah so i'm not gonna be messing with anything crazier just curios to see who gets hardcore and busts out the real acids.

_________________There's an old Italian saying, don't burn your tongue on another man's soup.

Tall Dark and Swarfy

Post subject: Re: Sulfamic Acid

Posted: Tue May 27, 2014 4:13 am

Joined: Wed Feb 20, 2013 2:22 amPosts: 987

COP<> Ferric Chloride is a popular etchant. Nitrates and nitrites passivate steel, as has been discovered by those who tame reactive knives with salami or corned beef (what I use). What I was trying to point you towards is rust bluing, which combines the two, adds nitric acid, and often throws in a secret sauce. The secret sauce isn't gonna be something easily sourceable.

The gunsmith solution is interesting, I would make sure its food safe before putting it to knives

Tall Dark and Swarfy

Post subject: Re: Sulfamic Acid

Posted: Wed May 28, 2014 3:51 am

Joined: Wed Feb 20, 2013 2:22 amPosts: 987

The formula I linked to should be food safe. Herter's original Belgian blue formula contains mercury salts. Not sure if any sticks around to play Mad Hatter after the distiller water boil, but I wouldn't chance it.

Cheers,

Rick

Jason B.

Post subject: Re: Sulfamic Acid

Posted: Wed May 28, 2014 2:56 pm

Joined: Tue May 29, 2012 12:29 amPosts: 1129

A blued knife is going to make food taste bad.

Tall Dark and Swarfy

Post subject: Re: Sulfamic Acid

Posted: Fri May 30, 2014 5:00 pm

Joined: Wed Feb 20, 2013 2:22 amPosts: 987

Jason<> Not poking a finger in your eye here, but do you have any experiences to back that up? Because chemically a rust blued knife should be identical to one with a natural patina.

If I get the urge I might try Mark Lee's Express Blue #1 on my white #2. When I get the MSDS I will post ingredients in this thread. Only problem is that the Sakai Yusuke isn't a problem child wrt reactivity (barely reactive) so I would only be doing it for aesthetics. And I don't want to dork up my new Kono Fuji. Hmm.

Cheers,

Rick

Jason B.

Post subject: Re: Sulfamic Acid

Posted: Sat May 31, 2014 10:53 pm

Joined: Tue May 29, 2012 12:29 amPosts: 1129

I can't speak for all bluing, I used cold blue many years and was unhappy with the overall results. I've use onions, lemons, vinegar and currently ferric chloride, I'm sticking with the ferric chloride.

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